BOGOTA, July 29 (Reuters) - Colombia's President Juan Manuel Santos said continuing attacks perpetrated by leftist FARC guerrillas, many of which target infrastructure, could bring an end to peace negotiations with the government.

Santos was re-elected in June with a mandate to complete a peace process with the FARC, or Revolutionary Armed Forces of Colombia. There have been negotiations in Havana since late 2012 even though the FARC refused to declare a lasting ceasefire.

"What we are saying to them is, keep this up and you are playing with fire and this (peace) process can end," Santos said at an industrial event.

The FARC have been fighting successive governments for 50 years in a conflict that has killed around 220,000 people and which mushroomed out of a peasant movement seeking land reform.

The United States and the European Union have declared the FARC a terrorist organization. (Reporting by Monica Garcia; Writing by Peter Murphy; Editing by Paul Tait)